https://journal.ugm.ac.id/v3/JCEF <p style="text-align: justify;">Journal of the Civil Engineering Forum (JCEF) is a four-monthly journal on Civil and Environmental Engineering related sciences. The JCEF is devoted to publish and disseminate research in the fields of structural engineering, geotechnical engineering, water resources engineering, environmental engineering, transportation engineering, and construction management.</p> <p style="text-align: justify;">The particular emphasis of JCEF is given to the civil &amp; environmental researches associated with disasters caused by natural hazards such as geo-disaster (earthquake, landslide, volcanic eruption), water-related disaster (flood, debris flow, coastal disaster, tsunami), and human-made hazards such as soil, water, and air pollution and water scarcity in a tropical region. Articles describing the topics of disaster risk reduction techniques, disaster early warning system, climate change adaptation, vulnerability analysis and trends, pre and/or post-disaster reconstruction and rehabilitation planning and management, forensic engineering, the socio-engineering approach for the countermeasures, or water reuse and recycle are particularly encouraged.</p> <p style="text-align: justify;">JCEF is open access journal and free of charge for submission, publication, and download. There are three categories of articles published in JCEF: Research Articles, Technical Notes, Editorial Note, and Review Articles. The article consists of 6 - 12 pages, 6 - 10 articles per issue, reviewed by selected peer-reviewers.</p> <p>&nbsp;</p> Department of Civil and Environmental Engineering, Faculty of Engineering, Universitas Gadjah Mada en-US Journal of the Civil Engineering Forum 2581-1037 <p>Copyright is granted to authors for the purpose of providing protection for articles written to describe experiments and their results. JCEF will protect and defend the work and reputation of the author and are also willing to address any allegations of violation, plagiarism, fraud, etc. against articles written and published by JCEF.&nbsp; JCEF is published under the terms of the&nbsp;<a href="http://creativecommons.org/licenses/by-sa/4.0/" target="_blank" rel="noopener">Creative Commons Attribution-ShareAlike 4.0 International License</a>&nbsp;(CC BY-SA 4.0). The author holds the copyright and assigns the journal rights to the first publication (online and print) of the work simultaneously.</p> https://journal.ugm.ac.id/v3/JCEF/article/view/26551 <p>Indonesia is highly vulnerable to earthquakes that can trigger soil liquefaction, particularly in coastal regions where saturated sandy soils with low relative densities are prevalent. This study investigated the influence of varying Class C fly ash contents (5%, 10%, and 15%), relative densities (50%, 70%, and 90%), and curing periods (7 and 14 days) on the unconfined compressive strength of fully saturated sandy soils as a liquefaction mitigation approach. The methodology included physical soil characterization, sample preparation with specific fly ash and relative density variations, and unconfined compressive strength testing after the curing period. The results demonstrated that increasing the fly ash content, relative density, and curing time significantly enhanced the strength of the samples. The highest strength occurred at 15% fly ash and 90% relative density, with 426.22 kPa (7 days) and 438.57 kPa (14 days). The most notable improvement occurred with an increase in fly ash content from 5% to 10% and relative density from 50% to 70%. Fly ash was more effective at enhancing the strength of sandy soil by promoting interparticle cementation, whereas excessive compaction tended to disrupt the soil structure and generate fine particles that reduced cohesion, as evidenced by the UCS test results and SEM observations. The most significant strength gain between 7 and 14 days was observed at 50% relative density and 5% fly ash, with a twofold increase. The combination of 10% fly ash and 70% relative density was optimal for field implementation, as it yielded strength values exceeding the liquefaction resistance thresholds, while maintaining practical compaction levels and material efficiency. A comparative cost assessment considering materials, labor, equipment, and construction time is recommended to evaluate the practical feasibility of fly ash stabilization relative to alternative ground improvement methods for Indonesian projects.</p> Yunan Yakuta Wangsawitana Muhammad Fauzan Heriansyah Putra Erizal Minson Simatupang Copyright (c) 2026 The Author(s) https://creativecommons.org/licenses/by-sa/4.0 2026-05-04 2026-05-04 293 304 10.22146/jcef.26551